twitter/bootstrap — comment on commit 39aca918d032fca589cbeb6c31cc3ef82684d0d0
File:  line 0
By lancehunt:

This change broke the less.js parser since less cannot accept mixins that have the same name as a class name (i.e. .clearfix and .clearfix() )

If you want to keep this, either rename your .clearfix() mixin or rename the .clearfix class name to something else.

See https://github.com/cloudhead/less.js/issues/413